Ferroelectric K0.5Na0.5NbO3 (KNN) thin films were prepared by a chemical solution deposition approach with polyvinylpyrrolidone (PVP) of different molecular weights introduced in the precursor solutions. The volatilization of the alkali ions and the effects of the molecular weight of PVP were examined with x-ray diffraction (XRD), thermal analysis, mass spectrometry, and x-ray photoelectron spectroscopy (XPS). The results clearly showed that the volatilization of the alkali ions mainly happened at moderate temperatures before the crystallization of the KNN perovskite phase. Loss of Na was more significant than K ions during the heating process of KNN. The introduction of PVP with the appropriate molecular weight could effectively promote the crystallization of the KNN perovskite phase at reduced temperature and substantially suppress the loss of the alkali ions before crystallization. Therefore, a high dielectric constant, piezoelectric coefficient, and well saturated ferroelectric hysteresis loops were obtained in the KNN films in which PVP of the right molecular weight were introduced.

Self-organized nanotubular layers are electrochemically fabricated on Ti–4Zr–22Nb–2Sn alloys in water/glycerol (volume ratio 1:1) mixtures containing 0.3 M NH4F. Highly ordered nanotubes with two distinct diameters of ∼203 ± 5 (large size) and 113 ± 5 nm (small size) were observed at the bottom of the layer, which may be ascribed to the different microstructure and composition in this alloy. On extended anodization, the small-size tubes gradually disappeared because of the increasing H+. After annealing for 1 h at 500 °C, the nanotube layer on the Ti–4Zr–22Nb–2Sn alloy was transformed from the amorphous phase to anatase. The nanotubes were connected to each other by spaced rings at the sidewalls, whereas the distance between neighboring rings increased with the amplitude of applied current density.

The morphology of the fracture surfaces of a bulk metallic glass (BMG) tested under compression was systematically studied. Experimental results showed that the fracture surface always comprises two kinds of zones, starting with a relatively smooth zone followed by the second zone with vein patterns. It implies strongly that the plastic deformation of BMGs always starts with a cooperative shear. The following catastrophic fracture characterized by the vein patterns may or may not occur, depending on the magnitude of this shear, which is controlled by the sample size and machine stiffness. This phenomenon was interpreted based on the temperature rise resulting from the work done during the cooperative shear. It revealed that for small samples, the shear is so small that the temperature increase is insignificant, accounting for the extensive serrated flow, while the temperature increase in samples beyond a critical size is sufficiently high so that the temperatures are higher than the glass transition temperature or even the melting temperature, leading to catastrophic fracture.

The unique structural, electronic, and mechanical properties of single-walled carbon nanotubes (SWNTs) have opened the doors to developments that push the limits of science. These advancements not only further scientific discovery, but also result in the development of everyday practical applications. These applications vary from singlemolecule sensors to nano-scaled transistors to multi-modal biosensors. This article focuses on three distinct developments made as a result of recent advances in spectroscopy of SWNTs. The first system examines the use of SWNTs for molecular detection using near-infrared light to produce tunable fluorescent sensors that are highly photostable. The second system examines the use of a 4-hydroxybenzene diazonium reagent to sort SWNTs based on electronic structure to create on-chip modifications of nano-electronic devices. The third system characterizes nanotube networks for such applications as flexible electronics, exploring the irreversible binding of adsorbates onto nanotube networks using electrical transport and Raman spectroscopy.

Biological materials have developed hierarchical and heterogeneous material microstructures and nanostructures to provide protection against environmental threats that, in turn, provide bioinspired clues to improve human body armor. In this study, we present a multiscale experimental and computational approach to investigate the anisotropic design principles of a ganoid scale of an ancient fish, Polypterus senegalus, which possesses a unique quad-layered structure at the micrometer scale with nanostructured material constituting each layer. The anisotropy of the outermost prismatic ganoine layer was investigated using instrumented nanoindentations and finite element analysis (FEA) simulations. Nanomechanical modeling was carried out to reveal the elastic-plastic mechanical anisotropy of the ganoine composite due to its unique nanostructure. Simulation results for nanoindentation representing ganoine alternatively with isotropic, anisotropic, and discrete material properties are compared to understand the apparent direction-independence of the anisotropic ganoine during indentation. By incorporating the estimated anisotropic mechanical properties of ganoine, microindentation on a quad-layered FEA model that is analogous to penetration biting events (potential threat) was performed and compared with the quad-layered FEA model with isotropic ganoine. The elastic-plastic anisotropy of the outmost ganoine layer enhances the load-dependent penetration resistance of the multilayered armor compared with the isotropic ganoine layer by (i) retaining the effective indentation modulus and hardness properties, (ii) enhancing the transmission of stress and dissipation to the underlying dentin layer, (iii) lowering the ganoine/dentin interfacial stresses and hence reducing any propensity toward delamination, (iv) retaining the suppression of catastrophic radial surface cracking, and favoring localized circumferential cracking, and (v) providing discrete structural pathways (interprism) for circumferential cracks to propagate normal to the surface for easy arrest by the underlying dentin layer and hence containing damage locally. These results indicate the potential to use anisotropy of the individual layers as a means for design optimization of hierarchically structured material systems for dissipative armor.

We report on the preparation of a bioactive CaO–SiO2 monolithic scaffold with interconnected bimodal nanomacro porosity, which simulates the morphology of a natural trabecular bone, by a newly developed modified sol-gel process. This method inherently creates nanopores, whose average diameter can be tailored to approximately 5–20 nm by solvent exchange. To achieve interconnected macroporosity (pores ∼5–300 μm in size), a polymer [poly(ethylene oxide)] is added, which causes phase separation simultaneously with the sol-gel transition. High-resolution scanning electron microscopy and mercury intrusion porosimetry demonstrate a high degree of three-dimensional interconnectivity and sharp distributions of pore size. In vitro bioactivity tests in simulated body fluid (SBF) show bioactivity of the material after soaking for approximately 5 h, as verified by the formation of a hydroxyapatite layer deep into the scaffold structure. Analysis of the SBF after the reaction indicates the dissolution of the samples, another desired feature of temporary scaffolds for bone regeneration. MG63 osteoblast-like cells seeded on our sol-gel glass samples responded better to samples with nanopores enlarged by a solvent exchange process than to the one with normal nanopores. Thus, the benefits of the high surface area achieved by sol-gel and solvent exchange procedures are most clearly demonstrated for the first time.